Conventionally, a projector type headlamp to be mounted on a vehicle such as an automobile has been known (e.g., see Patent Document 1). The projector type headlamp described in Patent Document 1 comprises a projection lens 300 (collimator lens) including a rotationally symmetric incident surface 310 that light from a light source (not illustrated) enters, and a rotationally symmetric spherical surface 320 irradiated with the incident light, as illustrated in FIG. 7.
As for the projector type headlamp of this kind, a projection lens with a novel design has recently been desired in terms of improving flexibility in vehicle design and the like. As the projection lens with the novel design, it can be considered that a projection lens which has a shape of an N-sided polygon (e.g., quadrilateral) in planar view or a shape similar to the N-sided polygon and has common edges (N edges) formed on the surface is configured.    Patent Document 1: Japanese Examined Application Publication No. 8-17045